Manufacture of seamless metal tubes



Dec. 3, 1957 c. BROOKS MANUFACTURE OF SEAMLESS METAL TUBES Filed Feb.23', 1954 R mm .1 5? a mm mm a? Q mm mm wmm g 8 3 I1 Q o E Ti 9 mm ow v3 1 Q3 TITJ/LTIAI 8 on on a E a mm m EH1 mm 2, 0: mm. m: @m T in sw F ki Q J mm P F M Q S Q 2 Q. N H mm mm 8 mm 8 a a 8 8 mm 2 \wmml UnitedStates Patent '0 MANUFACTURE OF SEAMLESS lvlETAL TUBES Cyril Brooks,Wolverhampton, England, assignor to The Wellman Smith Owen EngineeringCorporation Limited, London, England, a British company ApplicationFebruary 23, 1954, Serial No. 412,011

Claims priority, application Great Britain February 27, 1953 Claims.(CI. 8014) This invention relates to the manufacture of seamless metaltubes. More especially it is concerned with improvements in the controlof pilger mill operations.

In known pilger mill procedures, a heated open-ended cylindrical hollowor tube blank is placed on a mandrel and worked thereon between drivengrooved rolls having a peripheral gap. Under the action of the rolls,the mandrel is forced backward against resilient means, therebycompressing the latter, and when the gaps in the rolls come round to theblank in the revolution of the rolls, they release the grip of the rollsso that the resilient means reacts to return the mandrel. During thistime, the resilient means and the mandrel are fed steadily forwardtogether to move up a fresh part of the blank for treatment by therolls, the various operations being repeated until the treatment of theblank is completed. Provision is made to soften the arrest of the partssuddenly moved forward under the reactive impulse of the resilientmeans.

Suitably, a sort of dash-pot arrangement is used. Nevertheless, aconsiderable impact blow is experienced which adversely affects steadyforward feed of the blank. Arrangement is made, therefore, for thisimpact blow to be transmitted to hydraulic piston and cylinder apparatuscausing the hydraulic medium in this apparatus to be increased inpressure intensity. Restricted orifice release of the medium from suchapparatus is provided for to control the forward feed of the blank, thatis to say the steady feed of the mandrel in company with the resilientmeans as aforesaid. Moreover, it is known that the impact blow referredto tends to increase the restricted orifice outflow of the medium fromthe hydraulic piston and cylinder apparatus. The amount of this outflowat this time would permit feed of the blank at increased velocity wereit not for the fact that the resistance of the hydraulic piston andcylinder apparatus is arranged to be greater than the force, usuallyhydraulic, provided for that feed. The increased pressure intensityinduced in the hydraulic medium as stated, is of extremely shortduration and owing to this, and to the inertia of the hydraulic mass inthe hydraulic piston and cylinder apparatus being relatively great, thisapparatus rebounds, or tends to rebound, after the impact blow has beenimparted at the dash-pot. Consequently, the feed means for the blankbecomes arrested in its operation, or is slowed down. 0r sometimes, thismeans will be forced back. As a result, the desired constant incrementof feed distance of the blank per revolution of the pilger rolls hasbeen difiicult, if not impossible, to attain. Sometimes, a mechanicalcontrol, such as a screw and a co-operative nut which is rotated at aspeed suitably synchronised with the speed of the pilger rolls, isprovided to cause the feed means to move the lank forward by apre-determined distance per revolu- 'on of the pilger rolls. Suchmechanical control, however, creates much difliculty because of theheavy wear to which it becomes subjected, and because of the greatfricfiional heat generated because the nut and screw, as a re- .sult ofthe heavy loads imposed thereon.

2,814,962 Patented Dec. 3, 1957 An object of the present invention is toprovide a simple and reliable method of, and apparatus for, obtaining aconstant amount of forward movement of the blank per revolution of thepilger rolls.

According to one feature of this invention, a method of manufacture ofseamless metal tubes by pilger rolling wherein the impact blow,resulting from the sudden forward movement of the mandrel, under thereactive impulse of resilient means previously stressed during therolling, is transmitted to hydraulic piston and cylinder apparatus, ischaratcerised by the step of releasing hydraulic medium from saidhydraulic piston and cylinder apparatus in substantially preciselydetermined quantity per revolution of the pilger rolls.

According to another feature of the present invention, a pilger mill forthe manufacture of seamless metal tubes and comprising peripherallygrooved and gapped rolls, a carriage supporting resilient meanscomprising a part which is movable forward and backward on the carriageand-"supports the mandrel and a companion part which is fixed relativelyto the carriage, means for forward feed of the carriage, and hydraulicpiston and cylinder apparatus to which an impact blow on the carriage,as a result of sudden forward movement of the mandrel by reactiveimpulse of the resilient means, is transmitted when the gaps in therolls come round to the blank on the mandrel, is characterised by asecond hydraulic piston and cylinder apparatus having connections withthe one first-mentioned so as to receive hydraulic medium through saidconnection during forward feed of the carriage, and means operative todetermine substantially precisely the stroke of said second hydraulicpiston and cylinder apparatus, whereby the amount of feed of the tubeblank per revolution of the pilger rolls may be maintained substantiallyconstant.

The method of the invention may be carried out in such a way that anyoverstepping of the determined quantity of hydraulic medium releasedfrom the first hydraulic piston and cylinder apparatus due to the efiectof the impact blow referred to, may be taken up so that the determinedquantity, in the net result, is maintained substantially constant.

For this purpose, the apparatus may further comprise means whereby thepiston and cylinder components of the second hydraulic piston andcylinder apparatus may be further displaced relatively to each other atthe end of the determined stroke against the action of yieldable meansoperative to counteract the displacement. This yieldable means may be ofthe nature of a spring or of a constant pressure pneumatic or hydraulicpiston and cylinder apparatus.

In order to enable the invention to be readily understood, reference isdirected to the accompanying drawing in which:

Figure 1 is a sectional elevation of one example of apparatusconstructed in accordance with, and operative according to the methodof, the present improvements,

Figure 2 is partly a plan view of the apparatus and partly a sectionalelevation of the second hydraulic piston and cylinder apparatus thereof,and

Figure 3 is a fragmentary plan view illustrating a modification.

The apparatus shown in Figures 1 and 2, comprises a sole plate 10 fixedto the ground and a carriage 11 mounted to slide forward and backward onthe upper face of the sole plate and between guides 12 lying along eachside of such plate. A hydraulic cylinder 13 is disposed at the rear endof the sole plate 10 between a block 14 at that end and a fixed supportleg 15 further back. The piston 16 of the cylinder 13 is connected tothe rear end of the carriage 11 so that the cylinder, hereinafter termedthe feed cylinder, and its piston are operative to move the carriageforward. Rearward movement of the carriage is eifected by a hydraulicpiston and cylinder apparatus which suitably comprises a pair ofcylinders 17 disposed one along each side of the sole plate 1 above therespective guides 12 aforesaid. The pistons 18 of the cylinders 17 areconnected at their rear ends to a cross-head 19 on the carriage 11. Theupper part of the carriage is formed, forward of the cross-head, with anair chamber 20, and forward of that with a water brake chamber 21.Rearward of the cross-head 19 the carriage 11 has fixed thereon apedestal 22 housing a ratchet wheel 23 with multiple sets of teeth, thepedestal carrying a corresponding set of ratchet pawls 24. The ratchetwheel 23 is revoluble in bearings in the pedestal 22 and is fixed to ashaft 25 which extends forwardly through the cross-head 19 and into theair chamber 20 wherein it is slightly enlarged and formed with helicalgrooves at 26. The helically grooved part 26 engages in acorrespondingly grooved nut 27 fixed within the rear end of a hollowpiston 28 which has an external frusto-conical shoulder 29 at itsforward end. From this shoulder the piston is extended as a solid shaft30 to a mandrel head 31 slidable on the carriage 11 between guides 32.Forwardly of the mandrel head the shaft 30 is formed for connection tothe rear end of a mandrel 33 and carries a stripper block 34 for use instripping completed tubes from the mandrel. Forwardly of the sole plate1 is a pair of peripherally grooved pilger rolls 35 gapped at one partof the periphery in the well-known manner as at 36. A more or lesscylindrical recess 37, suitably slightly tapered as shown, is formed atthe forward end of the water chamber 21 to serve as a sort of dash-potfor the shouldered forward end 29 of the hollow piston. This recess 37is suitably provided in a liner 38 presenting a companion abutmentshoulder to the shoulder 29 on the hollow piston. When, in the operationof the pilger rolls 35 on a blank such as 39, disposed on the mandrel33, the latter is forced back, the hollow piston 28 moves over thehelically threaded part 26 of the ratchet-wheel shaft 25, and the nut 27in the rear end of the piston cooperates with the threads to cause thepiston and the ratchet wheel 23 to revolve so that a fresh part of theperiphery of the blank 39 is brought into position to be worked by therolls, the ratchet pawls 24 ensuring that this rotation is in onedirection only. The rearward movement of the hollow piston 28 causes theair in the piston and in the air chamber 20 to be compressed and thepiston 28, air chamber 20 and helically grooved part 26 of theratchet-wheel shaft 25 together constitute what is known in the art asresilient means. When the gaps 36 in the pilger rolls 35 come round tothe blank 39, the grip on the blank is released and the hollow piston 28and its shaft 30 are moved forward under the reactive force of the aircompressed in and by the hollow piston. The movement is sudden and thedash-pot 37 serves to brake it towards the forward end of the stroke.Nevertheless, an impact blow of considerable force comes on to thecarriage 11 when the shouldered part 29 of the piston 28 reaches thecorresponding shoulder in the forward end of the dash-pot. This impactblow is transmitted through the cross-head 19 to the pistons 18 of thehydraulic piston and cylinder apparatus 17, 18 which also serves toreturn the carriage 11 to its original position. During this returnmovement, the blank 39 is stripped from the mandrel 33 by the stripperblock 34 after the well-known manner. Independently of the forwardmovement of the blank 39 with the mandrel 33 under the reactive impulseof the resilient means, the mandrel .and resilient means are fed forwardtogether with the carriage 11 by the hydraulic feed cylinder 13 andpiston 16 and, of course, appropriate controls are provided for thishydraulic operation.

The pilger mill construction as thus far described provides foroperations of a nature well understood in the the abutment member 51.

art. In accordance with the present invention, a second hydraulic pistonand cylinder apparatus 40 is provided on a bed plate 41 fixed to theground. This apparatus comprises a pair of cylinders 42, 4-3 oppositelydisposed on a common axis and having communications at their inner ends,through suitable hydraulic connections 44, 45, 46 and a change-overvalve 47 and an adjustable stop valve 43, with a junction box 49connected by apprcpriate piping 50 with the inner ends of the cylinders17 of the first-mentioned hydraulic pistons and cylinder apparatus 17,18. The terms first and second hydraulic apparatus will be used forconvenience to designate the two hydraulic piston and cylinder appa=ratuses 17, 18 and 40 respectively. The piston 18 of the first hydraulicapparatus 17, 18 are connected to the cross-head 19 as above stated. Thepistons 52, 53 of the second hydraulic apparatus 40 are joined at theirouter ends by an abutment member 51 slidable on the bed plate betweentwo abutment surfaces 54, 55. The cylinders 42, 43 of this secondhydraulic apparatus 40 also are slidably mounted on the bed plate 41each between abutment surfaces 56, 57, but each is normally held againstone abutment 56 by the pressure exerted by a compression spring 58carried by the cylinder slides 59 or 60 and bearing on the otherabutment 57. If desired the compression springs 58 may be substituted byconstant pressure pneumatic or hydraulic piston and cylinder apparatusas will be understood. The travel of the abutment member 51 isdetermined by the thickness of a packer 61 inserted against one or theother of the corresponding abutment surfaces 54, (as shown, the abutmentsurface 55). Hydraulic pressure is transmitted to the cylinders of thesecond hydraulic apparatus from the cylinders of the first hydraulicapparatus through the junction box 49 and connections and valvesaforesaid. The change-over valve 47 operates to connect the cylinders42, 43 of the second hydraulic apparatus alternatively to the cylinders17 of the first hydraulic apparatus and to the exhaust connection 62.

In the operation of the mill, assuming a blank 39 to be applied to themandrel 33 and the pilger rolls 35 to be operating in normal manner, ashydraulic medium is supplied to the feed cylinder 13 to move thecarriage 11 forward, together with the resilient means, to feed a freshpart of the blank into the rolls, hydraulic medium in the cylinders 17of the first hydraulic apparatus is forced out through the piping 50 andthe movement of this medium is transmitted through the junction box 49and the connection 46 and appropriately adjusted stop valve 48 and thechange-over valve 47 to one or the other of the cylinders 42, 43, of thesecond hydraulic apparatus 40 according to the setting of the valve. Thepiston 52 or 53 of the latter cylinder is thus forced outwardly and itis so forced a distance determined by the movement of This distance, asalready indicated, depends on the thickness of the packer 61 aforesaid.Packers of different thicknesses are provided and the thickness of thepacker immediately in use is determined by the increment of feed desiredfor the size and weight of blank being milled. Appropriately, theabutment 55 against which the packer is placed may be used to determinethe distance which the abutment travels in one particular case, packersof suitable thicknesses being used at 61 for other cases. In any case,the distance is one which has previously been precisely determined aswill be understood. The second hydraulic apparatus 40, in effect,provides a measuring medium for determining the amount of hydraulicmedium discharged from the first hydraulic apparatus 17, 18.

When the piston of the second hydraulic apparatus 40, in action, hascarried the abutment member up to the packer 61, or the adjacentabutment 55, or to the other abutment 54 if the piston is being movedtoward that abutment, the travel of the feed cylinder piston 13, andthus the travel of the carriage 11, ceases and it does so until the gaps36 of the pilger rolls 35 come round to the blank and release theaforesaid resilient means. When that happens, the hollow piston 28 ofthe resilient means shoots forward through the water chamber 21 on thecarriage 11 and its shouldered end 29 enters the dashpot 37. This brakesthe reciprocatory parts and terminates in an impact blow on the shoulderof the dash-pot device. This blow, however, is transmitted through thecross-head 19 to the pistons 18 of the first hydraulic apparatus 17, 18.

Since the piston 52 or 53 of the second hydraulic apparatus 40, however,will have already reached the full limit of its travel in its cylinder42 or 43, any increase in hydraulic pressure intensity in the cylinders17 of the first hydraulic apparatus, following the impact blowtransmitted to the pistons 18 of the latter apparatus, will cause thecylinder 42 or 43 respectively of the piston and cylinder combination42, 52 or 43, 53 of the second hydraulic apparatus 40 to move along itsslide surface on the bed plate 41 and compress the spring 58 (orequivalent pneumatic or hydraulic apparatus) against which the movementof such combination will take place. This will allow the pistons 18 ofthe first hydraulic apparatus to move forward slightly, as well as thecarriage 11 and the feed cylinder piston 16. This movement, of course,must not be greater than an appropriate extent determined by themovements of feed given to the blank 39. It can be determined by anadjustable stop or by suitable packers or restraining bolts as will berealized.

After the dissipation of the energy resulting from the impact blow, thecompression spring 58 (or equivalent pneumatic or hydraulic apparatus)will return the cylinder 42 or 43 as the case may be so that a smallquantity of hydraulic medium will be returned from this cylinder 42 or43 of the second hydraulic apparatus 40 to the cylinders 17, of thefirst hydraulic apparatus. This will cause the pistons 18 of the latterapparatus to move back slightly and, correspondingly, the carriage 11and its feed piston 16. The net feed increment of the blank 39 perrevolution of the pilger rolls 35 will therefore be precisely thatdetermined by the initial movement of the immediately operative pistonof the second hydraulic apparatus 40 Suitably, the above return of eachcylinder of the sec-- ond hydraulic apparatus 40, is made to actuate anelectronic device (not shown) which, acting to control an electricsolenoid (or a thruster), operates the change-over valve 47 so that eachcylinder of this second hydraulic apparatus is used in turn.

For the purpose of enabling the first hydraulic apparatus 17, 18 to movethe carriage 11 backward to its original position and to effectstripping of the tube 39 from the mandrel 33, provision is suitably madefor highpressure hydraulic medium to be admitted to the storesaidjunction box 49, and thus to the inner end of the cylinders 17 of thishydraulic apparatus, through a hydraulic connector 63 under control of avalve 64. At this time, the adjustable stop valve 48 in the hydraulicconnections 46 to the second hydraulic apparatus 40 would be closed.

It will be realized that, by the invention, in spite of the impact blowreferred to, substantially constant increments of feed of the blank intothe rolls of the pilger mill is obtained with considerable advantage inthe pilger mill operations. Greatly improved consistency in the amountof material of the blank to be fed to the pilger rolls at eachrevolution of the rolls is obtained as will be understood.

As illustrated in Figure 3 the second hydraulic apparatus 40 may havethe pistons and cylinders duplicated, i. e. comprise oppositely arrangedpairs of hydraulic pistons 52a, 53a and cylinders 42a, 43a. The abutmentmember 57a in that case would suitably have the nature of a cross-headconnected across the ends of the pistons 52a, 53a the respective pairsof cylinders would have connections at 44a, 45a branched from theconnections 44, 45 aforesaid as is believed will be understood.

What I claim is:

1. In a brake-feeding mechanism of a pilger rolling mill, thecombination of a hydraulic forward feeding means operably connected to acarriage for forward movement, a braking means on said carriagecomprising a braking plunger and mandrel attached thereto which ismovable into a hydraulic braking space on said carriage to brake aforward movement of said mandrel and braking plunger, hydraulic reversemeans comprising a hydraulic piston and cylinder connected between abase and said carriage to provide a reverse carriage movement andoperative also to take up shock caused by the braking of said plunger insaid braking space upon forward release of the mandrel, a hydrauliclimiting means comprising a piston and cylinder which are connected withsaid hydraulic reverse means by a conduit so as to receive hydraulicmedium from the said hydraulic reverse means through said conduit duringoperation of said forward feeding means, stop means operativelyassociated with said limiting means to stop the same whereby the forwardfeed of the forward feeding means is maintained constant for eachrolling increment of the mill.

2. In the apparatus according to claim 1 wherein said conduit has anadjustable stop valve.

3. In the apparatus according to claim 1 wherein said limiting means hasyieldable means attached between said limiting means and a base toprovide an additional braking action operative when said limiting meansis stopped by said stop means.

4. Braking-feeding means according to claim 1 wherein the said hydrauliclimiting means comprises a pair of cylinders oppositely disposed on acommon axis and a change-over valve is provided in. said conduit betweensaid reverse means and said hydraulic limiting means to transmithydraulic pressure from the said reverse means alternately to theoppositely disposed cylinders of said hydraulic limiting means and thestop means to determine the stroke of the said hydraulic limiting meanscomprises a member connected with the pistons of said means andcooperative abutment surfaces lying at a predetermined fixed distanceapart on a base.

5. Braking-feeding means according to claim 1 wherein the said hydrauliclimiting means comprises a pair of cylinders oppositely disposed on acommon axis and a change-over valve is provided in said conduit betweensaid reverse means and said hydraulic limiting means to transmithydraulic pressure from the said reverse means alternately to theoppositely disposed cylinders of said hydraulic limiting means, and thestop means to determine the stroke of the said hydraulic limiting meanscomprises a member connected with the pistons of said means andcooperative abutment surfaces lying at a predetermined fixed distanceapart, and means for adjusting the said abutment surfaces.

References Cited in the file of this patent UNITED STATES PATENTS869,283 Winter Oct. 29, 1907 1,041,661 Nowak Oct. 15, 1912' 1,724,314Rober Aug. 13, 1929 1,833,990 Dreyer Dec. 1, 1931 1,936,475 Fritsch Nov.21, 1933 2,032,277 Gassen Feb. 25, 1936 2,090,535 Knoll Aug. 17, 1937

